75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
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// Copyright 2020 Google LLC.
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// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
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#include "tools/fiddle/examples.h"
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REG_FIDDLE_ANIMATED(Turtle, 256, 256, false, 0, 2) {
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// Simple turtle based graphics. The turtle starts out at 128, 128, looking North, pen down.
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// The input string is read left to right (but see 'r' below). Commands are a single character,
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// sometimes followed by additional arguments:
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//
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// u : Raises the pen
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// d : Lowers the pen
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// + : Reads integer N, rotates turtle N degrees clockwise
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// - : Reads integer N, rotates turtle N degrees counterclockwise
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// f : Reads integer N, moves turtle forwards N units
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// r : Reads integer N, then separator character C. C should be some non-digit, non-command
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// character. Repeats all commands after C until the next instance of C, N times. Can be
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// nested.
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//const char* input = "r2[r3(f50+90f50+90f50+90f50(+45uf50d[";
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//const char* input = "r360|f1+1|";
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const char* input = "uf100+91dr180|f3+2|+89uf60+90r2$f20-90dr60|f1+6|u-90f20$-90f50-90f30d+180f60uf1000";
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struct Turtle { float x; float y; float h; bool p; } t;
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const SkPaint& p() {
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static SkPaint paint;
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paint.setColor(SK_ColorBLACK);
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paint.setAntiAlias(true);
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paint.setStyle(SkPaint::kStroke_Style);
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paint.setStrokeWidth(0);
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return paint;
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}
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const char* eval(SkCanvas* canvas, const char* s, char e, float& dist, float& l, bool pt) {
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while (*s != e) {
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switch(*s++) {
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case 'u': t.p = false; break;
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case 'd': t.p = true; break;
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case '+': t.h += atoi(s); break;
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case '-': t.h -= atoi(s); break;
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case 'f': {
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float d = atoi(s);
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d = std::min(d, l);
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dist += d; l -= d;
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float r = t.h * 0.01745329f;
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auto s = sinf(r), c = cosf(r);
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Turtle nt = { t.x + s * d, t.y - c * d, t.h, t.p };
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if (pt && t.p) canvas->drawLine(t.x, t.y, nt.x, nt.y, p());
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t = nt;
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break;
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}
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case 'r': {
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int c = atoi(s);
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while (*s >= '0' && *s <= '9') { ++s; }
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auto n = s+1;
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for (int i = 0; i < c; ++i) { n = eval(canvas, s+1, *s, dist, l, pt); }
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s = n;
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}
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}
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}
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return s+1;
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}
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void draw(SkCanvas* canvas) {
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canvas->clear(SK_ColorWHITE);
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t = { 128, 128, 0, true };
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float totalDist = 0;
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float l = 1E9f;
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eval(canvas, input, 0, totalDist, l, false);
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l = frame * totalDist;
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t = { 128, 128, 0, true };
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eval(canvas, input, 0, totalDist, l, true);
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}
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} // END FIDDLE
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